Development of new experimental platform ‘MARS’—Multiple Artificial-gravity Research System—to elucidate the impacts of micro/partial gravity on mice

TLDR

The study aimed to investigate how partial gravity and microgravity affect mice using newly developed habitat cage units on the ISS centrifuge. Twelve C57BL/6J male mice were housed for 35 days under microgravity or artificial 1 g, with daily activity monitored via downlinked videos, then returned to Earth for analysis. Microgravity mice showed significant reductions in femur bone density and soleus/gastrocnemius muscle weight, whereas 1 g mice maintained levels comparable to ground controls, demonstrating that gravity prevents these losses and providing first evidence that the MARS platform can reveal molecular mechanisms of gravity regulation.

Abstract

Abstract This Japan Aerospace Exploration Agency project focused on elucidating the impacts of partial gravity (partial g ) and microgravity (μ g ) on mice using newly developed mouse habitat cage units (HCU) that can be installed in the Centrifuge-equipped Biological Experiment Facility in the International Space Station. In the first mission, 12 C57BL/6 J male mice were housed under μ g or artificial earth-gravity (1 g ). Mouse activity was monitored daily via downlinked videos; μ g mice floated inside the HCU, whereas artificial 1 g mice were on their feet on the floor. After 35 days of habitation, all mice were returned to the Earth and processed. Significant decreases were evident in femur bone density and the soleus/gastrocnemius muscle weights of μ g mice, whereas artificial 1 g mice maintained the same bone density and muscle weight as mice in the ground control experiment, in which housing conditions in the flight experiment were replicated. These data indicate that these changes were particularly because of gravity. They also present the first evidence that the addition of gravity can prevent decreases in bone density and muscle mass, and that the new platform ‘MARS’ may provide novel insights on the molecular-mechanisms regulating biological processes controlled by partial g /μ g .